1. Field of the Invention
The present invention relates to aircraft navigation. More particularly, the present invention relates to an improved aircraft navigation system and method for textually displaying an original flight plan and a modified flight plan simultaneously.
2. Description of the Related Art
Conventional flight planning systems provide a graphical representation of an active flight plan on a graphical display and a textual representation of the active flight plan on a separate Control Display Unit (CDU). The flight plan displayed on the CDU includes route information listing the waypoints and showing performance data, such as constraints and performance parameters, for each. The constraints include descent angle, speed, altitude, time, etc., and the performance parameters include course and distance information, expected time of arrival, fuel remaining, winds aloft, groundspeed, etc. The graphical display shows the active flight plan in two dimensions with the waypoints connected by a line showing the active flight route. For example, FIG. 1 shows a graphical display with the waypoints ABC, LL01, and LL03 connected by the active flight route 202.
The active flight plan can be modified by adding or deleting waypoints by interfacing with the CDU using a keyboard or by interfacing with the graphical display using a cursor control device. The graphical display is capable of showing the active flight plan and the modified flight plan in graphical form. For example, FIG. 2 shows a graphical display with an active flight plan 202 including the waypoints GUP, GUP44, and ABC and a modified flight plan 204 direct from the aircraft's present position (PPOS) to ABC. A solid line represents the active flight plan, and a dashed line represents the modified flight plan.
However, once modifications are made to the active flight plan, either textually or graphically, conventional systems and methods display only a modified flight plan on the CDU, and a comparison of the constraints and performance parameters for the active and modified flight plans is not possible. When only the modified flight plan is displayed, the performance data for the active flight plan is no longer available or even easily discernable.
For example, U.S. Pat. No. 5,715,163 relates to a cursor controlled navigation system for aircraft in which a flight plan can be modified by adding waypoints to either a graphical display or a CDU. However, when the desired (i.e., modified) flight plan returns to the original flight plan, waypoints that are not on the desired flight plan are deleted. With this system, it is not possible to provide a simultaneous display of the original and modified flight plans. A comparison of the constraints and performance parameters of both the modified and original flight plans therefore cannot be done.
There is a need, therefore, for an improved navigation system that simultaneously, textually presents the original and modified flight plans, including constraints and performance parameters, on a single display. Improvements for inputting modified flight plans are also desirable.